There are a number of things Mozilla is doing that are appealing to me as a power user.
1. Rust and Firefox Quantum. Mozilla has invested a herculean amount of effort into making Firefox's internals cutting edge, and we've only just started seeing it pay off. The updated CSS rendering component alone made Firefox one of the snappiest browsers, and it's going to get even faster as additional components are rewritten.
2. Firefox is going to start blocking a lot more trackers by default in the coming months; some of this is in beta, more is in nightly. Power users can already do this with extensions, but it's easier for me to recommend a browser that does it by default.
3. Mozilla is reviewing add-ons. There were a lot of complaints about this initially, but I feel safer installing things from Firefox Add-ons than I do from the Chrome Web Store. The review process isn't perfect, but it feels like it's much harder for a Firefox addon to scoop my entire browsing history and get away with it. Allowing me to disable automatic updates for individual extensions is also good; it's a second layer of protection against situations like that Sylish fiasco where an extension suddenly, silently becomes malicious.
4. Add-on APIs. The add-on situation was dire when Mozilla killed XUL extensions and switched to a Chrome-compatible format. But now they're extending it and adding all sorts of functionality for add-ons that Chrome doesn't have, again.